1. Field of the Invention
The present invention relates to a portable electronic device with High-Definition Multimedia Interface (HDMI), and more particularly to an apparatus and method for voltage controlling used in a portable electronic device.
2. Description of the Prior Art
The High-Definition Multimedia Interface (HDMI) is designed for the next generation of multimedia equipments and suitable for use in a digital television, DVD player, DVD recorder, personal video recorder (PVR), Set-Top Box (STB) and other digital AV products. The major feature of the HDMI is that the video and audio signals are transmitted simultaneously, which is distinct from the traditional manner where the video and audio signals are separately transmitted. The HDMI adopts non-compressed digital data transmission, thereby effectively reducing the signal interference and attenuation resulted from the digital and analog conversion.
In the HDMI specification, the HDMI includes a power pin which provides a power source of 5 volts. In an electronic device with the HDMI, when the power source of the electronic device is not 5 volts, a voltage conversion is needed to convert the power source to 5 volts, even though the electronic device is not connected to an external device through the HDMI. However, the voltage conversion will cause a loss of electric power. In particular, when the power source of the electronic device is a battery, such in the case of a mobile phone, digital player, notebook computer, etc., this loss of electric power will use up the battery power rapidly, and thus substantially shorten the use time of the electronic device.